This invention relates to a mechanism for latching together two objects, and, in particular, to a latch mechanism which can be mechanically unlatched either manually or automatically.
Latch mechanisms are employed in a wide range of products and provide a function of releasably holding or latching together two objects. For example, U.S. Pat. Nos. 3,848,907, 848,515, and 832,284 disclose different types of latch mechanisms employing resilient or leaf spring components. While perhaps useful to latch two objects together, these mechanisms are not particularly designed to unlatch when sufficient manual force is exerted to pull the latched objects apart, which is a desirable feature of a latch mechanism for use in some operations. In other devices such as that disclosed in U.S. Pat. No. 3,522,963, while manual unlatching of the latch mechanism is possible, the device does not adequately provide for an automatic unlatching or release of the latched component.
One well known type of product which includes a latch mechanism are hold open devices which may be utilized to maintain a door or other object in a selected position until a certain event occurs. Because in places such as hospitals many doors are desired to be kept open to allow easy passage therethrough, and because these doors are to automatically close during fires, door hold open devices are employed. A door is coupled by means of a rod to a portion of the latch mechanism of the door hold open device, and the latch mechanism is then latched, thereby maintaining the door in an open position. Upon a signal that smoke is present, the latch mechanism is automatically released, allowing the door to be biased closed to thereby contain the smoke and fire. Alternatively, hold open devices can be used as executive door releases. For instance, if an executive engages the latch mechanism and has a door propped open during a conversation with a client and realizes important matters are to be discussed, the latch mechanism of the door release can be remotely activated and thereby unlatched to allow the door to close automatically without the executive leaving his or her seat.
An existing problem with latch mechanisms such as those used in many door hold open devices results from the need to unlatch the latch mechanism both automatically and manually. While automatic unlatching upon a given condition may be the preferred mode of unlatching, it is often necessary to manually unlatch and then relatch the latch mechanism. For instance, and again considering door hold open devices used in hospitals, doors being held open must occasionally be closed to allow proper cleaning to be performed. Due to the configuration of some latch mechanisms, such as that disclosed in U.S. Pat. No. 5,140,173, the manual unlatching, and the subsequent relatching of the door hold open device to return the held door to the propped open position, may require an appreciable amount of force to be exerted or may possibly fatigue and wear away the latch mechanism. Thus, it is desirable to provide a latch mechanism which can be manually unlatched and relatched with a minimum of physical strength and effort, as well as be readily unlatched automatically if such an unlatching feature of the latching mechanism is desired.